When a table is created, it contains no data. The first thing
to do before a database can be of much use is to insert data.
Data is conceptually inserted one row at a time. Of course you
can also insert more than one row, but there is no way to insert
less than one row. Even if you know only some column values, a
complete row must be created.

To create a new row, use the INSERT command. The command requires the
table name and column values. For example, consider the products
table from Chapter 5:

The data values are listed in the order in which the columns
appear in the table, separated by commas. Usually, the data
values will be literals (constants), but scalar expressions are
also allowed.

The above syntax has the drawback that you need to know the
order of the columns in the table. To avoid this you can also
list the columns explicitly. For example, both of the following
commands have the same effect as the one above:

Tip: When inserting a lot of data at the same time,
considering using the COPY
command. It is not as flexible as the INSERT command, but is more efficient.
Refer to Section 14.4 for more
information on improving bulk loading performance.